Global Bifurcation Diagram for the Kerner-Konhauser Traffic Flow Model

We study traveling wave solutions of the Kerner-Konhauser PDE for traffic flow. By a standard change of variables, the problem is reduced to a dynamical system in the plane with three parameters. In a previous paper [Carrillo et al., 2010] it was shown that under general hypotheses on the fundamental diagram, the dynamical system has a surface of critical points showing either a fold or cusp catastrophe when projected under a two-dimensional plane of parameters named q(g)-v(g). In either case, a one parameter family of Takens-Bogdanov (TB) bifurcation takes place, and therefore local families of Hopf and homoclinic bifurcation arising from each TB point exist. Here, we prove the existence of a degenerate Takens-Bogdanov bifurcation (DTB) which in turn implies the existence of Generalized Hopf or Bautin bifurcations (GH). We describe numerically the global lines of bifurcations continued from the local ones, inside a cuspidal region of the parameter space. In particular, we compute the first Lyapunov exponent, and compare with the GH bifurcation curve. We present some families of stable limit cycles which are taken as initial conditions in the PDE leading to stable traveling waves.